Fast sqrt

[siberianstar]

Hello,

for the float type i've made

inline float fastsqrt(float c)
{
float output;
asm("sqrt.s %0,%1" : "=f" (output) : "f" (c));
return output;
}

but this does not work for double type. There is an asm instruction that is "sqrt.d" that is for double type, but if i try to compile:


inline double fastsqrt(double c)
{
double output;
asm("sqrt.d %0,%1" : "=f" (output) : "f" (c));
return output;
}

it gives operand error. Why ?

[jimparis]

The allegrex FPU doesn't do doubles

[ector]

If you're writing games, you don't need doubles. If you think you do, you're wrong :) That's why there is no hardware support.

[siberianstar]

sure.

I found in the MIPS R4000 manual that double were supported. After i read that psp has a custom cpu and there is no support for double.

[RATiX]

comparing squares is much more efficient than comparing roots.

[siberianstar]

i know =) don't take me like a stupid